Science - USA (2021-10-29)

maximum doping level and charge carrier
density of the polymer due to the existence of
(bi-)polarons ( 30 , 31 ). The plasmon resonance
is fully turned ON with the highest possible
modulation (red curve). The peak wavelength
shifts slightly blue to ~2.2mm. Notably, ap-
plying a negative voltage of−1 V (blue curve)
turns the antenna resonance entirely OFF, with

no remaining resonant light interaction. The

PEDOT:PSS is completely reduced (i.e., in

the neutral state) and hence is dielectric in

the studied IR spectral range.

The switching speed of our metallic polymer

nanoantennas is investigated in Fig. 2C. The

antennas are switched between ON and OFF

states at applied voltages of +1 V and−1V

while the transmitted intensity is recorded. The

bottom graphs (gray curves) show the voltage

applied to the polymer nanoantennas (±1 V),

and the corresponding modulated transmitted

intensity is depicted in the top graphs (green

curves). The left graphs in Fig. 2C illustrate

thefirst10switchingcyclesatafrequencyof

f= 1 Hz, confirming full transitions between the

614 29 OCTOBER 2021¥VOL 374 ISSUE 6567 science.orgSCIENCE

D

E

C F

A B

Fig. 3. Metallic polymer plasmonic metasurface for ultrahigh-contrast
active beam steering.(A) The metallic polymer metasurface is switchable
between the OFF state (−1 V, left) and the ON state (+1 V, right), thus allowing
beam steering with a 100% contrast ratio in the diffracted beam. (Band
C) Spectrum and SEM image of the pristine metasurface with a superperiod of
15 mm (diffraction anglef¼ 10 :2°,L= 380 nm,W= 160 nm,H= 90 nm,
Px,y= 500 nm). TM (transverse magnetic) plasmonic nanoantenna resonance
peaking at 2.65mm [laser wavelength in (D) to (F)]. (DandE) (Left) Schematics

of the measurement setup and beam-steering concept. The metasurface is

turned ON and OFF while the transmitted and diffracted beams are recorded

using an IR camera. (Right) Camera images and intensity profiles in the (D) ON

and (E) OFF states. The diffracted beam (right peak) at +10.2° vanishes

completely for−1V.(F) Selected IR camera images showing three cycles of

active beam steering when the applied voltage is cycled in situ between−1 V and

+1 V. The intensity of the diffracted beam (right spots) can be continuously

varied depending on the applied voltage. t, time.

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